Orthodontic brackets which are applied to teeth, either by attachment to a band or by direct bonding to a tooth, for the purpose of applying a moving force to the tooth to which the bracket is attached are known in the art. The moving force is generated by a wire attached to similar brackets attached to adjoining teeth. The moving force applied to teeth over a period of time permits the movement of the teeth to accomplish desired alignment of the teeth.
There are two major bracket designs for applying this moving force currently employed in the orthodontic field. The most common bracket is a bracket that does not have a vertical archwire slot, but rather a relatively wide, 0.100 to 0.165 inch, rectangular horizontal archwire slot that opens to the facial side of the bracket. This slot is referred to as the edgewise slot. The edgewise slot has gained dominance, to a large extent, due to the ease of attaching or removing the archwire. The archwire is captured in the edgewise slot by a relatively small gauge stainless steel tie wire (ligature tie) or by a small donut-shaped retaining member made from resilient rubber-like material (O-ring). Both the ligature tie and the O-ring can be easily placed and removed.
The other bracket design is one that has a relatively narrow, 0.050 to 0.065 inch, vertical opening archwire slot. It most commonly opens to the gingival side. This slot is referred to as the lightwire slot. In prior art, the archwire is captured and secured in the lightwire slot by a brass pin having an elongated body portion and an enlarged head portion. The pin is inserted into a slot in the body of the bracket, and thereby captures the archwire between the head of the pin and the body of the bracket. The pin is then secured to the bracket by bending the elongated portion of the pin over the body of the bracket. An example of such a bracket is shown in U.S. Pat. No. 3,178,821 (the disclosure of which is incorporated herein by referenced).
The prior art method of securing archwires in the lightwire slot with a brass pin can be somewhat difficult; however, the removal of the pin in many cases can be extremely difficult. In prior art orthodontic bracket designs, an O-ring cannot be used to secure an archwire in the lightwire slot. Typically, the O-ring will stretch and the archwire may become disengaged from the lightwire slot. A ligature tie can be used to secure an archwire in the lightwire slot. However, the ligature tie forces the archwire into the bottom of the slot and thereby destroys the vertical dimension of the lightwire slot which is essential for the slot to function properly.
Both the edgewise slot and the lightwire slot have advantages under different circumstances. Furthermore, both slots might be used together or individually on the same patient. Therefore, in addition to orthodontic brackets with only the edgewise slot or only the lightwire slot, there have been developed combination brackets. Such combination brackets permit the use of either the edgewise slot or the lightwire slot individually or in unison within the same bracket. Examples of such combination brackets are shown in U.S. Pat. Nos. 3,178,822; 3,163,933; 5,123,838 and 5,248,257 (the disclosures of which are all incorporated herein by reference).
Accordingly, there is a need for an orthodontic bracket which provides a vertical opening archwire slot designed in such a way as to make it relatively easy to secure archwires in those slots. Furthermore, there is a need for an orthodontic bracket having a vertical opening archwire slot designed in such a fashion as to make it relatively easy to remove an archwire from such a slot.